This invention relates to fluid pressure regulators and especially those used to regulate pressure in agricultural and turf irrigation systems.
It is well-known to use fluid pressure regulators in irrigation systems in order to provide substantially constant outlet pressure over a wide range of inlet pressures. The need for such regulators is particularly acute in low-pressure systems because slight variations in pressure cause a much greater variation than the same system operating at high pressure. Pressure regulators of this type are disclosed in commonly owned U.S. Pat. Nos. 5,875,815 and 5,257,646. Briefly, the '646 patent discloses a pressure regulator where higher than desired downstream pressure will cause sufficient pressure on an internal diaphragm, attached between a fixed liner in the regulator housing and the plunger, to move the plunger toward a valve seat to thereby reduce the flow through regulator and thus reduce downstream pressure. As downstream pressure decreases, a coil spring moves the plunger away from the valve seat, thereby increasing flow through the regulator. In this way, the pressure regulator plunger constantly seeks an equilibrium position that achieves substantially constant downstream pressure.